PROJECT SUMMARY Enhancing the effectiveness of smoking cessation interventions would significantly reduce premature deaths from lung cancer and other tobacco-related diseases. Smartphone apps for smoking cessation are one promising approach, as more smokers turn to their smartphones for assistance with quitting. However, these programs have high drop-out rates. The overall objective in this application is to develop a novel intervention to increase smoking cessation by engaging and retaining smokers in smartphone-based cessation interventions. The central hypothesis is that a cessation app with gamification?a motivational tool that uses non-monetary rewards to make behavior fun or playful?will increase engagement, retention, and quit rates relative to an app without gamification. Behavioral economics is an emerging field that can be leveraged to inform the design of a gamification intervention. The rationale is that determining the feasibility and early efficacy of a theory-informed gamification intervention will offer a strong scientific framework to develop new strategies for promoting smoking cessation. The central hypothesis will be tested by pursuing two specific aims: 1) Augment an existing smartphone cessation app with gamification to increase engagement and retention, and 2) Test the feasibility, engagement, retention, and early efficacy of the `gamified' app, compared to one without gamification. The goal of the first aim is to develop and test the feasibility and acceptability of a game-based design that will be informed by behavioral economic insights as well as iterative usability testing with smokers. It will be oriented around a series of 7-day challenges to stay abstinent. App users will accumulate points for engaging in specified activities within the app, and maintain an in-game avatar that will provide a visual representation of their progress in quitting. The goal of the second aim is to conduct a randomized pilot trial to test whether gamification enhances engagement, retention, and early efficacy of a smoking cessation app. A diverse sample of adult smokers recruited online will be randomized to an existing cessation app or to the existing app augmented with gamification. Participants will be assessed to determine differences in engagement, retention, and biochemically verified smoking status. The proposed research is innovative, because it focuses on a novel theory-informed intervention as a strategy to motivate smokers to stay engaged in a cessation program. The proposed research is significant, because it is expected to provide strong justification for the continued development and further evaluation of gamification approaches. Ultimately, such knowledge has the potential of offering new opportunities for the development of innovative strategies to improve smoking cessation interventions and reduce the risk of cancer and other illnesses attributable to tobacco among diverse populations.